Mesh: Avoid unnecessary normal calculation and dirty tags

This is mostly a cleanup to avoid hardcoding the eager calculation of
normals it isn't necessary, by reducing calls to `BKE_mesh_calc_normals`
and by removing calls to `BKE_mesh_normals_tag_dirty` when the mesh
is newly created and already has dirty normals anyway. This reduces
boilerplate code and makes the "dirty by default" state more clear.
Any regressions from this commit should be easy to fix, though the
lazy calculation is solid enough that none are expected.

13 files changed, 13 insertions, 28 deletions

diff --git a/source/blender/blenkernel/intern/cloth.c b/source/blender/blenkernel/intern/cloth.c
index f7454a02de6..0d6a0c045a5 100644
--- a/source/blender/blenkernel/intern/cloth.c
+++ b/source/blender/blenkernel/intern/cloth.c
@@ -1171,6 +1171,7 @@ static Mesh *cloth_make_rest_mesh(ClothModifierData *clmd, Mesh *mesh)
   for (unsigned i = 0; i < mesh->totvert; i++, verts++) {
     copy_v3_v3(mvert[i].co, verts->xrest);
   }
+  BKE_mesh_normals_tag_dirty(new_mesh);
 
   return new_mesh;
 }
@@ -1507,7 +1508,6 @@ static bool cloth_build_springs(ClothModifierData *clmd, Mesh *mesh)
     if (clmd->sim_parms->shapekey_rest &&
         !(clmd->sim_parms->flags & CLOTH_SIMSETTINGS_FLAG_DYNAMIC_BASEMESH)) {
       tmp_mesh = cloth_make_rest_mesh(clmd, mesh);
-      BKE_mesh_calc_normals(tmp_mesh);
     }
 
     EdgeSet *existing_vert_pairs = BLI_edgeset_new("cloth_sewing_edges_graph");
diff --git a/source/blender/blenkernel/intern/curve_to_mesh_convert.cc b/source/blender/blenkernel/intern/curve_to_mesh_convert.cc
index c48d155f5ce..d7fd8f7a2b6 100644
--- a/source/blender/blenkernel/intern/curve_to_mesh_convert.cc
+++ b/source/blender/blenkernel/intern/curve_to_mesh_convert.cc
@@ -649,7 +649,6 @@ Mesh *curve_to_mesh_sweep(const CurvesGeometry &main,
       offsets.vert.last(), offsets.edge.last(), 0, offsets.loop.last(), offsets.poly.last());
   mesh->flag |= ME_AUTOSMOOTH;
   mesh->smoothresh = DEG2RADF(180.0f);
-  BKE_mesh_normals_tag_dirty(mesh);
   MutableSpan<MVert> verts(mesh->mvert, mesh->totvert);
   MutableSpan<MEdge> edges(mesh->medge, mesh->totedge);
   MutableSpan<MLoop> loops(mesh->mloop, mesh->totloop);
diff --git a/source/blender/blenkernel/intern/displist.cc b/source/blender/blenkernel/intern/displist.cc
index 8c1161d6ff6..5caed6d6219 100644
--- a/source/blender/blenkernel/intern/displist.cc
+++ b/source/blender/blenkernel/intern/displist.cc
@@ -887,17 +887,11 @@ static GeometrySet curve_calc_modifiers_post(Depsgraph *depsgraph,
     if (mti->type == eModifierTypeType_OnlyDeform) {
       int totvert;
       float(*vertex_coords)[3] = BKE_mesh_vert_coords_alloc(mesh, &totvert);
-      if (mti->dependsOnNormals != nullptr && mti->dependsOnNormals(md)) {
-        BKE_mesh_vertex_normals_ensure(mesh);
-      }
       mti->deformVerts(md, &mectx_deform, mesh, vertex_coords, totvert);
       BKE_mesh_vert_coords_apply(mesh, vertex_coords);
       MEM_freeN(vertex_coords);
     }
     else {
-      if (mti->dependsOnNormals != nullptr && mti->dependsOnNormals(md)) {
-        BKE_mesh_vertex_normals_ensure(mesh);
-      }
       Mesh *output_mesh = mti->modifyMesh(md, &mectx_apply, mesh);
       if (mesh != output_mesh) {
         geometry_set.replace_mesh(output_mesh);
diff --git a/source/blender/blenkernel/intern/dynamicpaint.c b/source/blender/blenkernel/intern/dynamicpaint.c
index b85b2b3157c..01fd53d1ea2 100644
--- a/source/blender/blenkernel/intern/dynamicpaint.c
+++ b/source/blender/blenkernel/intern/dynamicpaint.c
@@ -1899,7 +1899,6 @@ static Mesh *dynamicPaint_Modifier_apply(DynamicPaintModifierData *pmd, Object *
       pmd->type == MOD_DYNAMICPAINT_TYPE_CANVAS) {
 
     DynamicPaintSurface *surface;
-    bool update_normals = false;
 
     /* loop through surfaces */
     for (surface = pmd->canvas->surfaces.first; surface; surface = surface->next) {
@@ -2018,21 +2017,17 @@ static Mesh *dynamicPaint_Modifier_apply(DynamicPaintModifierData *pmd, Object *
             settings.use_threading = (sData->total_points > 1000);
             BLI_task_parallel_range(
                 0, sData->total_points, &data, dynamic_paint_apply_surface_wave_cb, &settings);
-            update_normals = true;
+            BKE_mesh_normals_tag_dirty(mesh);
           }
 
           /* displace */
           if (surface->type == MOD_DPAINT_SURFACE_T_DISPLACE) {
             dynamicPaint_applySurfaceDisplace(surface, result);
-            update_normals = true;
+            BKE_mesh_normals_tag_dirty(mesh);
           }
         }
       }
     }
-
-    if (update_normals) {
-      BKE_mesh_normals_tag_dirty(result);
-    }
   }
   /* make a copy of mesh to use as brush data */
   else if (pmd->brush && pmd->type == MOD_DYNAMICPAINT_TYPE_BRUSH) {
diff --git a/source/blender/blenkernel/intern/fluid.c b/source/blender/blenkernel/intern/fluid.c
index efb33294efd..5de13fbdbed 100644
--- a/source/blender/blenkernel/intern/fluid.c
+++ b/source/blender/blenkernel/intern/fluid.c
@@ -3537,7 +3537,6 @@ static Mesh *create_smoke_geometry(FluidDomainSettings *fds, Mesh *orgmesh, Obje
   }
 
   BKE_mesh_calc_edges(result, false, false);
-  BKE_mesh_normals_tag_dirty(result);
   return result;
 }
 
diff --git a/source/blender/blenkernel/intern/mesh.cc b/source/blender/blenkernel/intern/mesh.cc
index 25d97d0bd3c..7f005fda6a5 100644
--- a/source/blender/blenkernel/intern/mesh.cc
+++ b/source/blender/blenkernel/intern/mesh.cc
@@ -1112,6 +1112,9 @@ Mesh *BKE_mesh_new_nomain_from_template_ex(const Mesh *me_src,
   mesh_ensure_cdlayers_primary(me_dst, do_tessface);
   BKE_mesh_update_customdata_pointers(me_dst, false);
 
+  /* Expect that normals aren't copied at all, since the destination mesh is new. */
+  BLI_assert(BKE_mesh_vertex_normals_are_dirty(me_dst));
+
   return me_dst;
 }
 
@@ -1688,6 +1691,7 @@ void BKE_mesh_transform(Mesh *me, const float mat[4][4], bool do_keys)
       mul_m3_v3(m3, *lnors);
     }
   }
+  BKE_mesh_normals_tag_dirty(me);
 }
 
 void BKE_mesh_translate(Mesh *me, const float offset[3], const bool do_keys)
diff --git a/source/blender/blenkernel/intern/mesh_boolean_convert.cc b/source/blender/blenkernel/intern/mesh_boolean_convert.cc
index eee1d3b9eec..3fcacb31b24 100644
--- a/source/blender/blenkernel/intern/mesh_boolean_convert.cc
+++ b/source/blender/blenkernel/intern/mesh_boolean_convert.cc
@@ -782,7 +782,6 @@ static Mesh *imesh_to_mesh(IMesh *im, MeshesToIMeshInfo &mim)
     }
   }
 
-  BKE_mesh_calc_normals(result);
   if (dbg_level > 0) {
     BKE_mesh_validate(result, true, true);
   }
diff --git a/source/blender/blenkernel/intern/mesh_convert.cc b/source/blender/blenkernel/intern/mesh_convert.cc
index ff953ef5b46..a289d208684 100644
--- a/source/blender/blenkernel/intern/mesh_convert.cc
+++ b/source/blender/blenkernel/intern/mesh_convert.cc
@@ -120,9 +120,6 @@ void BKE_mesh_from_metaball(ListBase *lb, Mesh *me)
     }
 
     BKE_mesh_update_customdata_pointers(me, true);
-
-    BKE_mesh_normals_tag_dirty(me);
-
     BKE_mesh_calc_edges(me, true, false);
   }
 }
@@ -514,7 +511,6 @@ Mesh *BKE_mesh_new_nomain_from_curve_displist(const Object *ob, const ListBase *
   }
 
   mesh = BKE_mesh_new_nomain(totvert, totedge, 0, totloop, totpoly);
-  BKE_mesh_normals_tag_dirty(mesh);
 
   if (totvert != 0) {
     memcpy(mesh->mvert, allvert, totvert * sizeof(MVert));
diff --git a/source/blender/blenkernel/intern/mesh_remesh_voxel.cc b/source/blender/blenkernel/intern/mesh_remesh_voxel.cc
index 7be4a6f2f94..02c9f61957d 100644
--- a/source/blender/blenkernel/intern/mesh_remesh_voxel.cc
+++ b/source/blender/blenkernel/intern/mesh_remesh_voxel.cc
@@ -140,7 +140,6 @@ static Mesh *remesh_quadriflow(const Mesh *input_mesh,
   }
 
   BKE_mesh_calc_edges(mesh, false, false);
-  BKE_mesh_calc_normals(mesh);
 
   MEM_freeN(qrd.out_faces);
   MEM_freeN(qrd.out_verts);
@@ -257,7 +256,6 @@ static Mesh *remesh_voxel_volume_to_mesh(const openvdb::FloatGrid::Ptr level_set
   }
 
   BKE_mesh_calc_edges(mesh, false, false);
-  BKE_mesh_normals_tag_dirty(mesh);
 
   return mesh;
 }
diff --git a/source/blender/blenkernel/intern/modifier.c b/source/blender/blenkernel/intern/modifier.c
index f4703b32582..e7ee8caf0eb 100644
--- a/source/blender/blenkernel/intern/modifier.c
+++ b/source/blender/blenkernel/intern/modifier.c
@@ -944,8 +944,10 @@ static void modwrap_dependsOnNormals(Mesh *me)
       break;
     }
     case ME_WRAPPER_TYPE_SUBD:
+      /* Not an expected case. */
+      break;
     case ME_WRAPPER_TYPE_MDATA:
-      BKE_mesh_calc_normals(me);
+      /* Normals are calculated lazily. */
       break;
   }
 }
@@ -992,7 +994,7 @@ void BKE_modifier_deform_vertsEM(ModifierData *md,
 {
   const ModifierTypeInfo *mti = BKE_modifier_get_info(md->type);
   if (me && mti->dependsOnNormals && mti->dependsOnNormals(md)) {
-    BKE_mesh_calc_normals(me);
+    modwrap_dependsOnNormals(me);
   }
   mti->deformVertsEM(md, ctx, em, me, vertexCos, numVerts);
 }
diff --git a/source/blender/blenkernel/intern/multires_reshape_apply_base.c b/source/blender/blenkernel/intern/multires_reshape_apply_base.c
index 65ba7b64d83..837b64affa8 100644
--- a/source/blender/blenkernel/intern/multires_reshape_apply_base.c
+++ b/source/blender/blenkernel/intern/multires_reshape_apply_base.c
@@ -156,7 +156,7 @@ void multires_reshape_apply_base_refit_base_mesh(MultiresReshapeContext *reshape
   /* Vertices were moved around, need to update normals after all the vertices are updated
    * Probably this is possible to do in the loop above, but this is rather tricky because
    * we don't know all needed vertices' coordinates there yet. */
-  BKE_mesh_calc_normals(base_mesh);
+  BKE_mesh_normals_tag_dirty(base_mesh);
 }
 
 void multires_reshape_apply_base_refine_from_base(MultiresReshapeContext *reshape_context)
diff --git a/source/blender/blenkernel/intern/subdiv_mesh.c b/source/blender/blenkernel/intern/subdiv_mesh.c
index 83e4336e3b1..83427adcb43 100644
--- a/source/blender/blenkernel/intern/subdiv_mesh.c
+++ b/source/blender/blenkernel/intern/subdiv_mesh.c
@@ -1155,7 +1155,7 @@ Mesh *BKE_subdiv_to_mesh(Subdiv *subdiv,
    * calculation. Since vertex normals are supposed to be a consistent cache, don't bother
    * calculating them here. The work may have been pointless anyway if the mesh is deformed or
    * changed afterwards. */
-  BKE_mesh_normals_tag_dirty(result);
+  BLI_assert(BKE_mesh_vertex_normals_are_dirty(result) || BKE_mesh_poly_normals_are_dirty(result));
   /* Free used memory. */
   subdiv_mesh_context_free(&subdiv_context);
   return result;
diff --git a/source/blender/blenkernel/intern/volume_to_mesh.cc b/source/blender/blenkernel/intern/volume_to_mesh.cc
index 8544d6c9c77..ef75d3d2482 100644
--- a/source/blender/blenkernel/intern/volume_to_mesh.cc
+++ b/source/blender/blenkernel/intern/volume_to_mesh.cc
@@ -183,7 +183,6 @@ Mesh *volume_to_mesh(const openvdb::GridBase &grid,
                               {mesh->mloop, mesh->totloop});
 
   BKE_mesh_calc_edges(mesh, false, false);
-  BKE_mesh_normals_tag_dirty(mesh);
 
   return mesh;
 }